ACS Weight & Balance 3 — Questions and Answers
Question 1: An aircraft weighs 3,200 lb with a CG at 95.0 inches. A 50 lb item is removed from a station 120.0 inches aft of datum. What is the new CG?
- 94.6 inches (Correct answer)
- 96.3 inches
- 93.1 inches
- 95.4 inches
Correct answer: 94.6 inches
New weight = 3,150 lb; Moment removed = 50×120 = 6,000; New moment = (3,200×95) – 6,000 = 298,000; CG = 298,000÷3,150 ≈ 94.6 inches.
Question 2: What is 'zero fuel weight'?
- Aircraft weight with all tanks empty
- Maximum allowable weight with no usable fuel on board (Correct answer)
- Weight of aircraft before fueling
- Empty weight minus unusable fuel
Correct answer: Maximum allowable weight with no usable fuel on board
Zero fuel weight is the maximum certificated weight of the aircraft without usable fuel, establishing structural limits for wing bending loads.
Question 3: When fuel is burned during flight, how does the CG typically shift in a high-wing aircraft with wing tanks?
- CG moves forward (Correct answer)
- CG moves aft
- CG moves up
- CG does not shift
Correct answer: CG moves forward
In most high-wing designs, wing fuel is located forward of the CG, so as fuel burns off, the CG moves forward.
Question 4: The term 'useful load' is defined as the difference between:
- Maximum gross weight and basic empty weight (Correct answer)
- Zero fuel weight and landing weight
- Ramp weight and takeoff weight
- Maximum takeoff weight and maximum landing weight
Correct answer: Maximum gross weight and basic empty weight
Useful load = Maximum Gross Weight – Basic Empty Weight, and represents the total payload the aircraft can carry.
Question 5: A helicopter weight and balance calculation differs from a fixed-wing calculation primarily because helicopters must also consider:
- Lateral CG limits in addition to longitudinal CG (Correct answer)
- Engine torque as a weight item
- Rotor blade weight separately
- Skid attachment point loads only
Correct answer: Lateral CG limits in addition to longitudinal CG
Helicopters have both longitudinal and lateral CG limits due to the need for cyclic trim authority, making lateral balance critical.
Question 6: What is the significance of the 'arm' in weight and balance calculations?
- The structural strength rating of a component attachment point
- The horizontal distance from the datum to a component's center of gravity (Correct answer)
- The vertical height of the CG above the ground
- The maximum load a station can support
Correct answer: The horizontal distance from the datum to a component's center of gravity
The arm is the horizontal distance measured from the datum to the point where the weight acts, used to compute moment.
Question 7: An aircraft has a MAC of 60 inches. The LEMAC is at fuselage station 128. If the CG is at station 146, what is the %MAC?
- 30% MAC (Correct answer)
- 36.7% MAC
- 30.0% MAC
- 18.0% MAC
Correct answer: 30% MAC
%MAC = ((CG station – LEMAC) ÷ MAC) × 100 = ((146 – 128) ÷ 60) × 100 = 30%.
ACS Weight & Balance 3
An aircraft weighs 3,200 lb with a CG at 95.0 inches.
A 50 lb item is removed from a station 120.0 inches aft of datum.
What is the new CG?